Process of treating ores by flotation.



I ill);

NIELS C. CHRISTENSEN, .OF SALT LAKE CITY, UTAH, ASSIGNOR TO METALLURGIC IMPROVEMENT CORPORATION, OF SALT LAKE CITY, UTAH, A'CORPORATION OF UTAH.

PROCESS OF TREATING ORES BY FLOTATION.

reenter.

No Drawing.

To all whom it may concern;

Be it known that 'l[, NIELs C. CHRISTEN- SEN, a citizen of the United States, residing at No. 637 E. 9 So.,.in Salt Lake City, in the county of Salt Lake and State of Utah, have invented new and useful Improvements in the Processes of Treating Ores by Flotation, of which the following is a specification.

This invention relates to a process for the treatment of copper ores and also ores containing copper and gold and silver. It is especially applicable to oxidized ores or ores which are partly oxidized. It is also applicable to sulfid ores which have been given a preliminary roasting treatment. Although the invention has been found especially applicable to relatively low grade copper ores, it is also applicable to many ores which contain silver and gold as well as copper.

The methods of applying my process are in some respects similar to the so-called flotation processes now so widely used, and may in part be carried out in the apparatus now used in these processes; my process, however, depends upon an entirel new dis covery. In my invention the valua le metal is separated by flotation, either by the frothing method now so widely used or by the film tension method as used by Macquisten; but the invention differs from the old flotation processes in that the metal is not floated as a 'sulfid but as an entirely different compound which must first be made from the minerals in the ore before treatment by flotation.

The compound of copper which possesses this property of floating to an even greater degree than the natural or artificially prepared sulfids is the. red cupro-cu ric sulfite such as is formed by boiling off the S0 from a solution of copper in water and S9,, or such as is made by the actionof 'CuFSO in a dilute SO solution upon the oxidized copper minerals, or by the action at proper temperature of SO gas and moisture upon the oxidized copper minerals. This bright red crystalline precipitate possesses this property of floating to'a remarkable degree. A qualitative test can readily be made in a test tube by boiling ofl the SO, from a solution of copper in Water and S0 cooling, adding a drop of oil, and shaking vigorous'ly. The .red sulfite is immediately carried to the surface by the bubbles, giving a bright red froth. This test may also be car- Specification of Letters Patent.

Patented Dec; 3, TOTE.

Application filed March 6, 1918. Serial No. 220,862.

ried out by pouring the precipitate and solution into a large watch glass where the sulfite may be made to float on the surface of the water by a little skilful manipulation of the glass. The precipitate can be made to do this even without the addition of oil, but more readil if alittle oil is present.

In apply-mg these facts to the treatment of an ore the copper values are converted to the cupro-cupric sulfite by a suitable method or the particles of copper mineral coated with the cupro-cupric sulfite by any suitable method and then the sulfite precipitate or sulfite coated mineral particles are removed from the gangue by flotation either by forming a froth, as is ordinarily done, or by gusing them to float away on the surface In a general way the process of my invention may be carried out as follows: If it is necessary to bring all the copper into solution as is the case with roasted pyrite ores containing copper and some oxidized ores in which the copper minerals are very intimately mixed with the gangue, the treatment may be as follows: The ore "ground to required fineness is agited with a solution of SO, in water until all the copper is brought into solution. The mixture is then heated torboiling and agitated until the excess S0, is driven off and the copper precipitated as the cupro-cupric sulfite. The mixture is then cooled and passed to the flotation machine and the sulfite separated from-the gangue in a manner similar to the sulfids in the well known sulfid flotation processes.

If it is necessary to bring only part of the copper into solution, the sulfitizing treatment may be as follows: The ore is agitated with a solutionof SO, in water'untilithe desired amount of copper has gone into solution. The excess S0 is then driven off and the dissolved copper precipitated as the cupro-cupric sulfite and the particles of the oxidized copper minerals are coated with Till]! the sulfite as shown in the following reaction wherein the expression CuO is used as a type radical to indicate the combined form of copper present in the mineral:

The cupro-cupric sulfite thus formed coats of a soluble lime compound will cause all theCuSO, formed to'be precipitated as the sulfite when the S is boiled off as shown- After the removalof the excess SO the pulp mixture is cooled and passed to the flotation machine as noted above.

It is advantageous to bring as little of the copper into solution as possible where the particles may be separated from the' gangue by grinding and may be coated with the sulfite and floated. In this case the moistened ore is treated at proper temperature with SO gas for a suflicient time to coat the particles with the sulfite and the is passed to the flotation machines as indicated above.

, A remarkable difl'erence in the appearance of this froth and that in the sulfid flotation process is that the froth in this case is a bright red. This is also the case with the film in the Macquisten tube wherethe concentrates floating 015? are a brilliant red.

Tests upon diflerent copper ores Joy-these methods have given most excellent results.

For example: An ore carrying 40% copper as carbonate in a sandstone, after a preliminary treatment of only five minutes and driving off the excess 80,, vgave a recovery of 95% and a concentrate carrying 26% copper before cleaning or re-treatment; a complex silicious iron ore carrying 1% copper and some gold and silver, after ten minutes treatment and boiling, gave an extraction of 85% upon the gold, silver, and

copper, in a concentrate carrying 12% copper; a heavy iron sulfid ore carrying 2% copper after roasting and thirty minutes preliminary treatment and boiling gave an extraction of 90%.

. I have also found that the gold and silver values present'are caused to float by this treatment of oxidized ores. It is probable that the silver is changed to the sulfid in the boiling operation, especially if the ore contains much iron which would go into solution. N 0 special reason can be assigned for the floating-of the gold in this case except that it is probably brightened-in thepreliminary treatment so as to float readily. It is a fact, however, that some ores which do not yield to flotation of the gold and silver by the ordinary methods have given excellent results by this process. Other methods of converting the copper to the sulfite or coating the copper minerals with the sulfite maybe used, such as treatment wlth a soluble sulfite like calcium bisulfite, or precipitating the Cu from a sulfate solution by means of calcium bisulfite;

but these have not given as good results as the method outlined. As it is obviously imscope and spirit of the claims hereunto appended. Moreover, as all the methods of treating the pulp after the sulfitizing treatment can obviously not be covered in a brief specification, I wish it understood that I desire to be limited here also only by the scope and spirit of the appended claims, the sulfite precipitate and the coated mineral' particles, or'in other words the sulfitized minerals, may be separated from the gangue by any of the well known froth or film flotation methods by any of the ordinary mechanical appliances successfully used in the old sulfid flotation processes.

It will be apparent to all'metallurgists that this discovery has a wide field of application. Among these applications the following may be mentioned, namely, the treatment of:

Partly oxidized copper ores. The sulfitizing treatment of these ores not only causes the oxidized minerals to float, but also cleans the sulfids so that they float more readily.

Oxidized copper ores in sandstone or other non-soluble gangue. These ores yield very readily to this treatment and give a high extraction and a very clean concentrate.

Heavy iron sulfid ores. By roasting these ores they may be handled without difliculty,

.the S0 from the roast being absorbed in suitable towers and used as the solvent, or sulfitizing agent, and the heat from the roasting operation being used to drive off the excess S0 Many of the ores in these different classes which carry the gold and silver in the sulfids are advantageously treated by this process, the sulfids being cleaned and caused to float more readily by the-treatment.

Some of these ores carrying gold and silver along with the copper will give good extractions on the gold and silver as well as the copper.

In the claims I have used the term flotation to cover all of the well known methods of flotation either by the frothing or film methods. The term flotation has come. into such general use and is so well knownlthat it may be and is commonly used in a general way to cover any of the processes or methods by which a mineral compound is separated from the gangue by virtue of its particles not being wet by water to the same degree as the gangue, of adhering to bubbles of air, of being wet by oils to a much greater degree than the gangue, etc., which properties make it possible to separate these mineral particles from the gangue by floating them away on the surface film of water or floating away attached to bubbles, or removing in a froth. The fiotative properties of the sulfids are now well known and the processes which make use of these properties to separate the sulfids are called flotation processes and the act is called flotation. 4 7

It is in the broad general sense whose application is now so generally acknowledged and understood that 'I use the term flotas tion in the claims. The newly discovered flotative properties of the sulfites are similar to those of the sulfids and any method for using these properties to sepa-.

rate this compound from the gangue is flotation.

Having described my discovery and outlined its applications, what I claim and desire to patent is:

1. The process of concentrating ores which comprises separating cupro-cupric sulfite by flotation.

2. The process of concentrating ores which comprises converting copper minerals therein into cupro-cupric sulfite and separating said converted minerals by flotation.

3. The process of concentrating ores which comprises converting copper minerals therein superficially i-nto cupro-cupric sulfite'and separating said converted minerals by flotation.

4. The process of treating copper-containing comminuted ores which comprises subjecting said ores to the action of sulfur dioxid in the presence of water, thereby forming copper sulfite, and heating, thereby forming cupro-cupric sulfite.

5. The process of treating copper-containing comminuted ores which comprises agitating said ores with an aqueous solution of sulfurous acid and subsequently heating, thereby expelling sulfur dioxid and forming cupro-cupric sulfite.

6. The process of treatin"copper-containing comminuted ores whici comprises agitating said ores with an aqueous solution of sulfurous acid to effect complete solution of the copper and subsequently heating, thereby expelling sulfur dioxid' and forming cupro-cupric sulfite.

7. The process of treating copper-containing ores which comprises subjecting said ores to the action of sulfur dioxid in the presence of water and in the absence of air, thereby avoiding formation of copper sulfate, and subsequently heating, thereby expelling sulfur dioxid and forming cuprocupric sulfite.

8. The process of treatin copper-containing comminuted ores whic comprises agitating said ores with an aqueous solution of sulfur dioxid, thereby forming copperfsulfite, adding a soluble lime compound and subsequently heating, thereby expelling sulfur dioxid and forming cupro-cupric sulfite.

9. The process of treating copper-containing comminuted ores which comprises subjecting said ores to the action of sulfur dioxid in the presence of water, thereby forming copper sulfite, and heating, thereby forming cupro-eupric sulfite, and separating said cupro-cupric sulfite by flotation.

10. The process of treating copper-containing comminuted ores which comprises agitating said ores with an aqueous solution of sulfurous acid and subsequently heating, thereby expelling sulfur dioxid and forming cupro-cupric sulfite, and separating said cup'ro-cupricsulfite by flotation.

11. The process of treating copper-containing comminuted ores wh1ch comprises a 'itatlng said ores with an aqueous solution of sulfurous acid to effect complete solution 'cupro-cupric sulfite by flotation.

12. The process of treating copper-containing ores which comprises subjecting said ores to the action of sulfur dioxid in the presence of water and in the absence of air, thereby avoiding formation of copper sulfate, and subsequently heating, thereby expelling sulfur dioxid and forming cuprpcupric sulfite, and separating said cuprocupric sulfite by flotation.

13. The process of treating copper-containing comminuted ores which comprises agitating said ores with an aqueous solution of sulfur dioxid, thereb forming copper sulfite, adding a soluble lime compound and subsequently heating, thereby expelling sulfur dioxid and forming cupro-cupric sulfite,

flotation.

In testimony whereof I have signed my.

name to this specification.

mans o. CHRISTENSEN. 

